Increased structural damage caused by earthquakes on hilltops and along ridges has often been related to amplification of ground motion due to the presence of topography. However, comparison between ... [more ▼]

Increased structural damage caused by earthquakes on hilltops and along ridges has often been related to amplification of ground motion due to the presence of topography. However, comparison between observations and numerical modeling has shown that amplification is only partly dependent on the prominent surface morphology. Strong effects are also induced by soft layers, such as weathered rock material or colluvium, covering the topographies. Numerous seismically triggered landslides are reported to occur in the same materials that are likely to amplify ground motions. Therefore, it can be suspected that ground motion dynamics significantly contribute to the observed slopes failures. This potential relationship is the subject of the present case study, the Ananevo rockslide in the northeastern Tien Shan mountains. The survey included geophysical prospecting, earthquake recordings and structural analyses of the rock fabric. On the basis of the field data, observed amplification effects could be related to the local geological conditions and particularly to the surface morphology and to the presence of low-velocity layers-deeply weathered rocks-on the top of the bedrock. Surface layer- and topography-dependent amplification has also been studied numerically by 2D and 3D finite element modeling of ground motion dynamics. The present paper focuses on additional effects that may be induced by the presence of a fault zone and of the landslide scarp. Further, observed and computed ground motion dynamics are connected with slope failure susceptibility: 2D numerical simulations reveal that strain localization is closely related to wave amplification in surficial low-velocity layers, particularly below convex surface morphologies. [less ▲]

New probabilistic seismic hazard and Arias Intensity maps have been developed for the territory of the Kyrgyz Republic and bordering regions. Data were mainly taken from the seismic catalogue of ... [more ▼]

New probabilistic seismic hazard and Arias Intensity maps have been developed for the territory of the Kyrgyz Republic and bordering regions. Data were mainly taken from the seismic catalogue of Kyrgyzstan and partly from the world seismic catalogue. On the base of seismicity and active tectonics, seismic zones were outlined over the area. For these, Gutenberg-Richter laws were defined using mainly instrumental data, but regarding also historical events. Attenuation of acceleration inside the target area could not be determined experimentally since existing strong motion data are insufficient. Therefore, empirical laws defined for other territories, principally Europe and China, were applied to the present hazard computations. Final maps were calculated with the SEISRISKIII program according to EUROCODE8 criteria, i.e. for a period of 50 years with 90% probability of non-exceedance. For long-term prediction, 100 years maps with 90% probability of non-exceedance have been developed. The procedure used for seismic hazard prediction in terms of PGA (Peak Ground Acceleration) was also applied to Arias intensities in order to be able to define regional seismogenic landslide hazard maps. [less ▲]